Former president Donald J. Trump won the Iowa caucuses on Monday, with The Associated Press calling the race for Mr. Trump less than an hour after caucusing began. The state Republican party is reporting precinct-level results. This is the most detailed vote data available for the first 2024 presidential election contest.

The map above shows the leading candidate in each precinct. It is shaded according to the number of votes per square mile for that candidate, meaning sparsely populated areas where fewer caucusgoers live are lighter, and denser areas are darker.

How the top three candidates are doing in each precinct

Here’s another way to look at the results. In the maps below, precincts are shaded according to each candidate’s vote share for the three top candidates — Mr. Trump, Nikki Haley, the former South Carolina governor, and Gov. Ron DeSantis of Florida.

How Republicans are voting in different kinds of areas

This table shows the leading candidate in precincts that have reported votes, based on the demographics of those areas.

Trump’s support

Mr. Trump improved significantly on his performance in the Iowa caucuses in 2016, when he received 24.3 percent of the vote, losing to Ted Cruz, who received 27.6 percent. Mr. Trump gained ground in many kinds of areas, but most of all in areas with lower average incomes and fewer college graduates.

Each dot in the charts below represents one neighborhood’s caucus precinct. The dots are positioned on the charts based on the percentage of the vote each candidate received in that precinct.

Mr. Trump’s strength on Monday has cut across many different kinds of areas. His lead is most pronounced in areas with fewer college-educated voters.

DeSantis’s support

Mr. DeSantis is a distant second, trailing Mr. Trump by double digits. Mr. DeSantis, despite campaigning in all 99 Iowa counties, and earning the endorsement of key state officials and religious leaders, has not found consistent pockets of support among key demographic groups.

Haley’s support

Ms. Haley has performed her best in areas that are wealthier and have a higher concentration of college-educated voters. These include precincts that surround cities like Des Moines and Iowa City.